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RCA BTA-1R 160,80m conversion.




 
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Author Topic: RCA BTA-1R 160,80m conversion.  (Read 509 times)
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Ac8wp
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« on: May 23, 2019, 07:50:48 PM »

Hello all. I have 2 rca bta-1r transmitters of which I would like to convert to 160m and 75m. I was wondering if anyone had a tank curcuit design that I could use? I planned on not using a band switch and just using 1 transmitter for each band. Im new with designing tank curcuit's so any info anyone can provide would be much appreciated.
Thanks
AC8WP
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WA1HZK
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« Reply #1 on: May 24, 2019, 05:42:26 PM »

Similar Project

https://www.youtube.com/watch?v=cqM-nbiMBOE

http://www.arrl.org/news/arrl-repurposes-am-broadcast-transmitter-for-ham-radio-use

I used the parts for my Homebrew 75 meter rig.
Keith
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KL7OF
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« Reply #2 on: May 25, 2019, 09:58:50 AM »

I have a BTA-1S  converted to 160 meters..The original slug-tuned final tank had been on fire.  It evidently got so far out of tune that the coil heated to the point that the fibreglas spreader bars ignited.  The tank was replaced with a Pi-setup...some coil stock and a Johnson breadslicer...The 4-400 final tubes work to full output. The modulator tubes were changed out to 813's (didn't have any 4-400s) and an external  PP-2A3 speech amp to drive them.  The RF driver was also Kaput so the driver tube was reworked into a buffer stage and driven with a homebrew VFO.
All the original iron is being used including the filament transformers for the 4-400 modulators being reconfigured to provide 10V for the 813's.  This transmitter came out of a Montana Mom and Pop station and was brought back to life by KF7EH..It has been in my shack for about 10 yrs..
   I would think you could use the original tank coil and a suitable cap (values in the handbook), eliminate the slug setup and your RCA would easily convert to 160 meters.
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KB5MD
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« Reply #3 on: May 26, 2019, 01:31:11 PM »

300pf vacuum cap for tuning......b&w 850a inductor....2000pf bread slicer for loading.  All wired in standard pi-output
shorten all the leads to and from components in pi network and you can bandswitch from 80 meters and 40 meters .
I have a BTA 1R1 that I use this way and it works quite well.
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Ac8wp
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« Reply #4 on: June 04, 2019, 10:54:10 PM »

So when calculating the plate load resistance using  Rl=Ep/(k x Ip) do i use the plate current for 1 tube or do I use the combined current consumption since the 4-400a's are in parallel?  
AC8WP
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DMOD
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« Reply #5 on: June 04, 2019, 11:10:54 PM »

Total current of both.


Phil - AC0OB
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